The invention relates to an electrofilter for the removal of dust from gases which are at pressures of up to 30 bar and temperatures of up to 500.degree. C.
Examples of the removal of dust from gases in the above-named pressure and temperature range are the pressure gasification of coal and low-temperature coal distillation processes. The gases produced as reaction product in such processes at high temperature and pressure are preferably further processed or utilized without losses of pressure or temperature, but first impurities have to be removed from them. Owing to the nature of the process of the pressure gasification of coal the product gas carries ash particles which have to be removed. In the low-temperature distillation process it is often necessary to perform a dry gas cleaning in a fluidized bed, followed by removal of dust in the electrofilter. Clearly, specially designed electrofilters are needed for such applications.
Insofar as it can be seen, no electrofilter has ever yet been disclosed in which all of the constructional and functional difficulties arising from the pressure and temperature levels have been satisfactorily solved. It has been proposed to purify gases at high pressure in an electrofilter in which the casing itself consists of a thick-walled tube and serves as the precipitating electrode (DE-PS 565 063), or to purify high-temperature gases by means of tubular precipitating electrodes which are designed to carry a flowing coolant (DE-OS 27 55 059). The first proposal is not unconditionally suitable for high temperatures, and also it is uneconomical for large quantities of gas. The second proposal is not designed for the case in which a high pressure is simultaneously present, and it entails unnecessarily high heat losses.
The problem thus exists of devising an electrofilter which will be suitable for the removal of dust from gases at a pressure of up to 30 bar and a temperature up to 500.degree. C., and which can be constructed and operated at economically acceptable cost.